Recently, cultivation of low potassium vegetables are spotlighted as high added value vegetables cultivated at plant factories. The number of patients being restricted to intake potassium by the doctor, for example, artificial dialysis patients, chronic nephropathy patients, or the like, is said to be about 300,000 in Japan, and the potential demand for low potassium vegetables has been high. As such, it is conceived that low potassium vegetables are attracting attention.
As potassium has long been known as one of the three major nutrients for plants, it is essential for the plant growth and is always contained in vegetables. For this reason, supply of vegetables having low potassium content is desired by patients under potassium intake restriction and medical personnel.
Up to now, methods far cultivating low potassium spinach and other leafy vegetables have been disclosed as the methods for providing vegetables having low potassium content e.g., Patent Literatures 1 to 3).
According to the prior art literatures, low potassium containing vegetables were made available by cultivating with potassium containing hydroponic solution, and subsequently cultivating with potassium-free hydroponic solution which does not contain potassium but includes sodium instead or cultivating with hydroponic solution not including potassium or sodium. For example, the following Patent Literature 1 discloses a method for cultivating low potassium spinach by specifying the periods during which the spinach is cultivated with potassium containing hydroponic solution and potassium-free hydroponic solution.